Dust covers the belongings of a Syrian family inside a house on March 4, 2017 following reported government airstrike on the rebel- held town of Douma, on the eastern outskirts of the capital Damascus a day earlier. (Photo by Abd Doumany/AFP Photo)

A boy rests over furniture stacked over a pick-up truck while driving through a damaged neighbourhood in the northern Syrian town of al-Bab, Syria March 4, 2017. (Photo by Khalil Ashawi/Reuters)

A member of the Syrian Civil Defence volunteers, also known as the White Helmets, carries a wounded girl amid the rubble following reported government airstrike on the rebel- held town of Douma, on the eastern outskirts of the capital Damascus, on February 25, 2017. Syrian regime forces carried out raids on several areas in the country, targeting mainly the besieged town of Douma, causing the deaths of at least 13 civilians, according to Syrian Observatory for Human Rights. (Photo by Sameer Al-Doumy/AFP Photo)

A convoy carrying military aid to the Syrian Democratic Forces (SDF) drive near the northeastern Syrian city of Hasaka, Syria February 24, 2017. (Photo by Rodi Said/Reuters)

A damaged classroom is pictured after airstrikes in the rebel held besieged Douma neighbourhood of Damascus, Syria February 25, 2017. (Photo by Bassam Khabieh/Reuters)

People walk on the rubble of a damaged school after airstrikes in the rebel held besieged Douma neighbourhood of Damascus, Syria February 25, 2017. (Photo by Bassam Khabieh/Reuters)

People walk at an area hit by airstrikes in the rebel held besieged Douma neighbourhood of Damascus, Syria February 25, 2017. (Photo by Bassam Khabieh/Reuters)

A man walks at a site hit by airstrikes in the rebel held besieged Douma neighbourhood of Damascus, Syria February 25, 2017. (Photo by Bassam Khabieh/Reuters)

Civil defence members try to put out a fire at a site hit by airstrikes in the rebel-controlled town of Ariha in Idlib province, Syria February 25, 2017. (Photo by Ammar Abdullah/Reuters)

A man walks at a site hit by airstrikes in the rebel-controlled town of Ariha in Idlib province, Syria February 25, 2017. (Photo by Ammar Abdullah/Reuters)

Civil defence members work at a site hit by airstrikes in the rebel-controlled town of Ariha in Idlib province, Syria February 25, 2017. (Photo by Ammar Abdullah/Reuters)

People salvage goods from a market after airstrikes in the rebel-controlled town of Ariha in Idlib province, Syria February 25, 2017. (Photo by Ammar Abdullah/Reuters)

A man tries to put out a fire at a site hit by airstrikes in the rebel held besieged Douma neighbourhood of Damascus, Syria, February 26, 2017. (Photo by Bassam Khabieh/Reuters)

A civil defence member works amid burning vehicles at a site hit by airstrikes in the rebel held besieged Douma neighbourhood of Damascus, Syria, February 26, 2017. (Photo by Bassam Khabieh/Reuters)

Civil defence members try to put out a fire at a site hit by airstrikes in the rebel held besieged Douma neighbourhood of Damascus, Syria, February 26, 2017. (Photo by Bassam Khabieh/Reuters)

Free Syrian Army fighters man a checkpoint on the eastern edge of the northern Syrian town of al-Bab, Syria, February 27, 2017. (Photo by Khalil Ashawi/Reuters)

A Free Syrian Army fighter mans a checkpoint on the eastern edge of the northern Syrian town of al-Bab, Syria, February 27, 2017. (Photo by Khalil Ashawi/Reuters)

Free Syrian Army fighters stand near an ambulance on the eastern edge of the northern Syrian town of al-Bab, Syria, February 27, 2017. (Photo by Khalil Ashawi/Reuters)

Free Syrian Army fighters help an injured fellow fighter on the eastern edge of the northern Syrian town of al-Bab, Syria, February 27, 2017. (Photo by Khalil Ashawi/Reuters)

A rebel fighter reacts carrying his weapon near damaged buildings in the northern Syrian town of al-Bab, Syria February 28, 2017. (Photo by Khalil Ashawi/Reuters)

A Syrian family drives a vehicle in the northern Syrian town of al-Bab, Syria February 28, 2017. (Photo by Khalil Ashawi/Reuters)

A Syrian family drives a vehicle in the northern Syrian town of al-Bab, Syria February 28, 2017. (Photo by Khalil Ashawi/Reuters)

People walk amidst rubble of damaged buildings in the northern Syrian town of al-Bab, Syria February 28, 2017. (Photo by Khalil Ashawi/Reuters)

Damaged seats are pictured amidst rubble of buildings in the northern Syrian town of al-Bab, Syria February 28, 2017. (Photo by Khalil Ashawi/Reuters)

People ride motorcycles amidst the rubble of damaged buildings in the northern Syrian town of al-Bab, Syria, February 28, 2017. (Photo by Khalil Ashawi/Reuters)

A Syrian family drives a vehicle in the northern Syrian town of al-Bab, Syria, February 28, 2017. (Photo by Khalil Ashawi/Reuters)

A girl stands amidst the rubble of damaged buildings in the northern Syrian town of al-Bab, Syria, February 28, 2017. (Photo by Khalil Ashawi/Reuters)

A man rides a motorcycle while carrying his weapon near damaged buildings in the northern Syrian town of al-Bab, Syria, February 28, 2017. (Photo by Khalil Ashawi/Reuters)

A boy pushes a tire along a street in the Syrian rebel-held town of al-Rai, Syria March 2, 2017. (Photo by Khalil Ashawi/Reuters)

Turkish military vehicles drive in the Syrian rebel-held town of al-Rai, as they head towards the northern Syrian town of al-Bab, Syria March 2, 2017. (Photo by Khalil Ashawi/Reuters)

Rebel fighters carry a platter of rice with meat during a feast to celebrate taking over al-Bab town, in al-Rai town, northern Aleppo countryside, Syria March 3, 2017. (Photo by Khalil Ashawi/Reuters)

Syrian men and Civil Defence volunteers, also known as the White Helmets, extinguish fire following reported government airstrike on the rebel-held town of Douma, on the eastern outskirts of the capital Damascus, on February 26, 2017. Government raids continue despite the United Nations confirmation a few days earlier that Moscow formally asked its ally Damascus to stop launching strikes during the Geneva negotiations, which began earlier in the week. (Photo by Abd Doumany/AFP Photo)